Ultra-Thin Rechargeable Lithium Ion Batteries on Flexible Polymer: Design, Low Temperature Fabrication and Characterization

Abstract

In this work we developed flexible rechargeable thin film lithium ion batteries based on all-solid-state materials. The flexible batteries were fabricated using low temperature sequential physical vapor deposition techniques. A thin film battery (TFB) architecture consisting of Ti/V 2 O 5 /LiPON/Li/encapsulation multilayer was deposited on flexible polyimide substrate. To the best of our knowledge, the obtained TFBs are among the thinnest reported with an overall thickness of 50 μm including substrate, active layers and encapsulation stack. The fabricated TFBs delivered discharge capacity as high as 0.15 mAh (1.5 cm 2 of cathode area) upon galvanostatic cycling at 30 μA.cm −2 within 3.8-1.5 V voltage range. The capacity decreased during cycling with an average fading rate of 0.25% over 100 cycles. Electrochemical impedance spectroscopy (PEIS) measurements and modeling analysis revealed an increase of the internal resistance during cycling. Furthermore, it was shown that the internal resistance increase was induced by a progressive decrease of the electrolyte/electrodes contact area. TFBs having the same architecture and cell design were fabricated on two substrates: a flexible polyimide foil and a rigid silicon wafer. Electrochemical characterization showed a clear influence of substrate type on TFBs discharge capacity and internal resistance variations during cycling, the results are discussed within this paper

Physical Vapor Deposition in Solid‐State Battery Development: From Materials to Devices

“…While during cycling with an upper cut-off voltage of 5.5 V severe degradation over the first 20 cycles was observed, cycling to lower cut-off voltages (1.4 V) showed improved cycling behavior when the upper cut-off voltage was set to 5.0 V. The battery had a capacity of about 170.7 𝜇Ah cm −2 µm −1 (362.5 mAh g −1 ) with a capacity retention of 99.85% within the first 100 cycles in the voltage range between 1.4 and 5.0 V. [122] Flexible Cells: Future applications, such as wearable electronics, might require flexible batteries. Several flexible cells have been realized on polymer substrates, for example, polyimide, [148,262,263] and inorganic materials, such as thin and flexible YSZ sheets [264] and mica layers. [265] On polyimide substrates either amorphous cathodes, for example, MoO 3 or V 2 O 5 , or LFP annealed at 400 °C were employed.…”

“…Future applications, such as wearable electronics, might require flexible batteries. Several flexible cells have been realized on polymer substrates, for example, polyimide, [ 148,262,263 ] and inorganic materials, such as thin and flexible YSZ sheets [ 264 ] and mica layers. [ 265 ] On polyimide substrates either amorphous cathodes, for example, MoO 3 or V 2 O 5 , or LFP annealed at 400 °C were employed.…”